The arrival
of warm April days marks
the emergence of the new queens, born and mated the previous autumn. They survive the
harsh winter in rotten wood or the soil, their metabolism slowed down to a
minimum. They also produce Glycerol, which acts as an antifreeze! After emerging their first task is to
undertake investigation flights to find a suitable nesting-place and food in the form of
tree sap and insects.

natural tree cavity

Since natural tree cavities are becoming rare, they often use human
habitation such as old sheds, behind the wood boarding of terraces and balconies, loft
spaces and alike.

Hornet nest in the roller-shutter cabinet

When the queen has decided on a nesting-place, she first makes a small pedicel (stalk) from which the nest will be
suspended. The first cell are built outwardly from it and are soon all occupied with eggs. After five to eight days small larva (quantity 1-2mm) develop,
which during the coming twelve to fourteen days pass through five larval stages.

larva head

They are held in by a sticky
secretion initially and later by their sheer bulk pushing against the cells.

When fully
grown the larva produce a fine silk thread, from a special gland, to cover the
cell. So protected, the hornet pupae metamorphose during the coming thirteen to fifteen
days.

The young hornet then bites its way out of the cell. The newly eclosed
worker will then rest, in an apparently idle fashion, in the cell from which it has emerged.

However, even this seems to
perform an important function by warming surrounding larvae, aiding there
development.

In this way, workers of
Vespa crabro vexator are capable of increasing the temperature
of surrounding cells from 21° C to 31° C in 6 minutes.

Building material, contrary to other "general forage loads" such as
water, carbohydrate-rich juices, and proteins in the form of insect prey, is not shared with other female workers in the nest. The foragers continue to process
it and then add the building material to the nest structure themselves. A freshly emerged female worker (who does not go on foraging trips yet) can not,
therefore, do construction work at the nest for this period.

Workers will stay in the nest for two to three days before taking theirfirst flight. Around this time a paper sleeve is started, which will eventually cover and protect the cells. Each worker
cell can be reused up to four times.

After five to ten female workers have emerged, the queen starts to fly from the nest less and less, with the workers taking over the role of foraging. Workers are noticeably smaller (18-25mm) than
the queen (35mm), and only live for three to four weeks. Eventually the queen becomes nest bound and will never
leave the nest again. With queen safely hidden in the nest, the most
dangerous time for the colony has now passed. The queen now focuses solely
on reproduction, the function she will perform until her demise at the
end of the season.

Hornet-queen with workers (her daughters), busy feeding and maintaining the starting cells (the queen
is the larger wasp in the centre).

If you think these are large: In parts of Asia and Japan Vespa mandarinia occurs, a close relatives of our hornet which is twice the size!

More workers must be raised to allow the colony to grow. They work tirelessly collecting food, building materials and water.Hornets
continue to forage, even at night during humid, windless weather!

Hornets are attracted to bright lights like moths causing them to become disorientated. As a result, they often
crash against window panes sometimes scaring the people inside. By turning out the light the however they are able to rapidly reorientate and will move on. Hornets are capable of
flying with light intensity of 0,01 Lux, at which the human eye is completely useless.

On warm summer days, the workers moisten the surface of the cells with water and so lower the
temperature through evaporative cooling. After completing the first comb a new pedicel is built to allow construction of a new tier. Construction occurs basically downwards from
the first comb, with additional lateral expansion of each comb and the paper.

"Kindergarten" of the
hornets (the larvae and the covered pupae can be seen clearly)

Hornets and other social wasps use paper (wood
pulp) to construct their nests. In other words: they use rotten wood as the main building material for the nest. They scrape it from worn and weathered wooden
fences, buildings, telephone poles, and other sources. They mix this with saliva and chew it up into a ball with
their mandibles (mouth parts). This makes the wood fiber extremely soft and moist. After a period of chewing, the hornet adds the paste to the nest
structure and spreads it out with her mandibles and legs. After it thoroughly dries; a type of tough, durable paper is formed.

The stripy pattern produced on the comb is characteristic of the hornet, each different coloured stripe representing the pulp
from a different tree.

If sufficient material is
collected to the nest one flies and one further-builds at cells or nest covering; the
saliva of the animals serves thereby as adhesive. This soft mass dries very fast to a
paper-like layer.

The strongly structured nest - covering with its fine grain and the
numerous shell-like formed out air bags - reminds of veneer wood from different wood.

The cells of the hornets are a true miracle of nature, whose building method has been passed genetically from generation to
generation for millions of years.

Nutrition of the brood and final development of the nest

Large nests of hornets capture thousands of insects each day!

The hornet is essentially a predator of a
wide variety of insects.

Hornets dismember captured insects with their powerful mandibles removing head, legs, wings and abdomen. Only the
thorax, with the proteinaceous flight musculature, is transported as little meatballs to the nest and fed to the larvae.

Larvae are nourished by the adults with this mixture of
captured insects, paralyzed and masticated, which they regurgitate.

During periods of bad weather, the larvae can feed the workers with a sugary solution.

The larvae form a living food-store, which can help balance out the ebb and flow of supply to the colony (like honey in
bees). Such food exchange between individuals is termed "trophallaxis".

The queen needs more protein than the workers to develop her ovaries to producing eggs. The highly active workers need
mainly only carbohydrates. This they obtain these sugary liquids from damaged trees which seep sap, particularly oaks and ashes.

In addition they eat the juice of ripe fruits:
sap, juices of ripe fruits: apples, pears, plums and nectar. Hornets forage up to 1500 m from their nest.

Hornet feeding on fruit, the
three simple eyes "Ocelli", arranged in a triangle can be seen clearly. Two
color forms of hornet occur in Germany. The hornet shown in the photo, which carries a red
"V" on the thorax, is Vespa crabro germana which is found in the west and south.

The other form, "Vespa crabro
crabro" predominantly inhabits the north and the east of Germany.

Unlike wasps, hornets don't plague picnic areas in the summer in search of food. There is thus no danger of being stung in
the throat by a hornet!

In the absence of natural nest-cavities, hornet-queens sometimes
settle in the spring in bird nest-boxes, although these rarely offer enough space for a
mature hornet colony. By the early summer, with 25 to 30 workers and three to four combs
such boxes are full. Thus the only possibility is to build outside the box or look
elsewhere. In the latter case, workers fly out to search for suitable sites in the
neighbouring area. If successful, some female workers fly with the queen to a
new, larger cavity where a new secondary nest is established.

This process is called
"relocation".

Workers fly between the new and the
old nest tending for both. The brood in the old nest are raised to adulthood while the construction of the new nest is underway. Eventually all the hornets move to the new
secondary nest and the old nest becomes disused. How exactly the hornets are able to direct each other to the new nest site remains a mystery, although chemical signals are
probably used.

In the time between mid August and mid September, the hornet colony
achieves its developmental peak, amounting to 400 - 700 animals and a 60 cm high
nest. The queen now lays eggs, which become males (also called drones, quantity 21-28mm) and young queens.

Mating of
the new queens and their hibernation

The appearance of the first sexuals (queens and males) indicates the decline of the colony. The workers gradually neglect the
old queen and she eventually leaves the nest and, exhausted from oviposition, dies.

The workers are now busy feeding the sexuals with protein and carbohydrates. This provides the
young queens with the necessary reserves for the long hibernation phase.

The sexuals do
not take part in the work, just sit on the comb and feed. At this stage unemerged larvae
have no chance to develop and lose weight eventually falling from their cells.

On beautiful autumn days, the
sexuals swarm out to mate.

They collect by trees or close to the nest. After
mating, males die quickly.

The inseminated young queens now hunt for a suitable hibernation
place. With a short life span, the last female workers die at the beginning of November and with them
the last activity in the nest.

Old nests are never resettled the
following year. Many young hornet-queens do not make it through the winter falling victim
to fungal attack or predation by insectivores.